1. Field of the Invention
The present invention relates to a shape measuring apparatus and a shape measuring method for measuring a shape of an edge surface of a thin sample such as a semiconductor wafer, an aluminum substrate or glass substrate for a hard disc, or the like.
2. Description of the Related Art
An edge (marginal portion) of a wafer may be damaged or cracked during manufacturing of a semiconductor wafer or during manufacturing of a device using a wafer by contacting another part or a wafer holding member. Moreover, due to the damage or crack thereof, the wafer may be broken. It is considered that the occurrence of the damage or crack of the edge of the wafer relates to a shape of the edge of the wafer. Therefore, it is important to measure an edge profile of a thin sample (plate-like sample), an example of which is a wafer. Note that a shape of an edge surface described here refers to a profile of a wafer in the thickness direction (one-dimensional direction), that is a shape of a thickness direction cross section, and hereinafter referred to as an edge profile.
On the other hand, a technique is disclosed in ““measuring apparatus of edge-notch shape of wafer” electronic materials, 1997 August issue” (hereinafter, referred to as “Non-Patent Document 1”) in which a light is emitted from one side of a wafer among both sides between which a marginal portion of the wafer is sandwiched, an image of a projection image of the wafer is taken by a camera disposed at another side, and an edge profile of the wafer is measured by the shape (outline) of the image obtained thereby.
Further, in Japanese Unexamined Patent Application Publication No. 10-267636 (hereinafter, referred to as “Patent Document 1”), a surface inspection device is disclosed in which a light is emitted toward a surface (mirror surface) of a sample while changing an angle of the sample, an image of the reflected light reflected only in the coaxial direction with respect to the emitting direction is obtained through a telecentric lens, and an angle distribution of a surface of the sample, that is a shape of a surface of the sample is measured from the obtained image.
However, in the shape measuring of a projection type as shown in Non-Patent Document 1, there is a problem in that an edge profile can not be measured in the case where a measurement site for the edge profile has a dimple shape where projection light (emitted light) will not reach. For example, a cutout portion of a hemicycle so called a notch indicating a crystal orientation of a wafer is formed therein. However, the edge profile of the notch portion can not be measured in the shape measurement of the projection type disclosed in Non-Patent Document 1.
In addition, as disclosed in Patent Document 1, the measurement in which reflected light reflected in the coaxial direction with respect to the emitting direction of light is detected while changing an angle of a sample is applied to the measurement of a small surface angel distribution caused by a small concavity and convexity of a surface of a sample. When the measurement technology shown in Patent Document 1 is applied to measurement of edge profile, inclination of the sample needs to be changed each time light is emitted to a plurality of measurement points at which surface angle is to be obtained. Therefore, there is a problem in that it is difficult as a matter of practice to apply the measurement technique disclosed in Patent Document 1 to the measurement of the edge profile in which a shape having surface angles which varies approximately 180° is measured, because there are disincentives, for example, a support mechanism for a sample becomes complicated.
Accordingly, the present invention has been made in the light of the circumstances described above, and is aimed at providing a shape measuring apparatus and a shape measuring method suited for measuring an edge profile (a cross section shape of an edge surface in thickness direction) of a thin sample such as a semiconductor wafer or the like.